The present invention relates to air velocity measurement and, more specifically to portable units for measuring the velocity of air entering or leaving outlets of heating, ventilating or air conditioning systems.
In order to achieve a desired balance of air discharged from, or exhausted into, the diffusers, registers, grills or other such openings in a heating, ventilating or air conditioning system it is necessary to measure the velocity of air entering or leaving each such opening. So-called balancing hoods are commonly provided to measure air flow through openings by placing an open end of the hood over the opening in sealing relation to the surrounding surface. All air flowing through the opening is thus forced to pass through flow measuring apparatus associated with the hood. Often the apparatus senses the total pressure developed by the air flowing through the hood, or measure the velocity at one point in the hood, and from this provides a scale reading in flow rate proportioned to the pressure or flow. The balancing hoods are intended to be hand-held over the openings through which flow is being measured and are therefore lightweight and portable in construction. However, such units are rarely of a reliably high degree of accuracy and, at least, represent only a close approximation of the actual velocity or quantity of air flowing through the opening.
It is a principal object of the present invention to provide a portable device for measuring air flow through a vent opening with a high degree of accuracy and reliability.
A further object is to provide portable air flow measuring apparatus wherein air flow is sampled at a plurality of positions distributed over a cross section of the flow path and measured in a manner providing a true indication of total air flow.
Another object is to provide air flow measuring equipment which advantageously employs averaging principles previously used in permanently installed pressure measuring systems in a portable, lightweight, air flow collecting and velocity measuring device.
Other objects will in part be obvious and will in part appear hereinafter.